Map projections . and corner of the map. We shall compute other projections for this same case ofa map of Europe, and be able to compare their relative merits. A concise idea of the variation of scale along the parallel isgiven by the following small table for the three cases of standardparallels 22|°, 450, 67^. Scale along the parallel. Simple conic. Parallel 0O=22j° 00 = 45° 0o = 67i° O0 I-074 10 I-023 1-156 20 IOOI i-oSi — SO I 009 1-030 — 40 1*054 1-004 1*080 50 1-151 1-004 1-034 60 — 1-044 1-007 70 — 1-165 1 001 So 1-043 OF PROJECTIONS Simple conical projection with two standard parallels
Map projections . and corner of the map. We shall compute other projections for this same case ofa map of Europe, and be able to compare their relative merits. A concise idea of the variation of scale along the parallel isgiven by the following small table for the three cases of standardparallels 22|°, 450, 67^. Scale along the parallel. Simple conic. Parallel 0O=22j° 00 = 45° 0o = 67i° O0 I-074 10 I-023 1-156 20 IOOI i-oSi — SO I 009 1-030 — 40 1*054 1-004 1*080 50 1-151 1-004 1-034 60 — 1-044 1-007 70 — 1-165 1 001 So 1-043 OF PROJECTIONS Simple conical projection with two standard parallels andtrue meridians. Let A A, BB, be elements of the two standard parallels, ofthe same extent in longitude. We have to choose 0, the poleof the projection, in such a way that A A, BB shall be arcs ofcircles concentric at 0; shall subtend the same angle at 0; andshall be their true distances apart. OA _AA _cos(j)1 OB ~ BB ~ cos2 OA cos $, We have Hence OA — OB cos <bx — cos (b2. and Fig. 14. Conic with two Standard Parallels. COS <£j rl=OA=R(.2-(bl) 2 sin ——- sin r —*-= •OX which is the expression for the radius of the standard the constant of the cone we have r, .6 = R cos (b1. AX, whence H. M. p. = 6_ A\ <£._, — $1 . - fa) { COS fa — COS fa r ^R(fa~ ) COS ftl - (<ftl - 0) COS 02 COS fa — COS fa In practice we may draw a standard parallel by computa-tion from (i) and then construct the projection as the simpleconic with one standard parallel was constructed, by laying offalong the central meridian and one standard parallel the truedistances taken from geodetic tables. The scale along the meridians, and along the standardparallels, is true. The scale along any other parallel of latitude 0 is rd6 nr R cos
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Keywords: ., bookcentury1900, bookdecade1910, bookpublisherlondo, bookyear1912
